Since I’ve been talking about sentient animals in cartoons, what about Scooby-Doo? Here we have a group of kids constantly proving that the supernatural is actually just groundskeepers with a grudge and access to expensive projectors, yet they take for granted the fact that their dog can talk.
With a strong canine accent, certainly, but still in recognizable English. Wouldn’t you think that’s just as supernatural as a ghost? Not in that universe, I suppose. Or does Scooby really talk at all? Maybe it’s just a hallucination brought on by Shaggy’s constant drug use. Assuming that what we hear is totally accurate, however, Scooby is apparently in some sort of state between Pluto and Goofy. Then we have his nephew Scrappy-Doo, who speaks perfect English. It’s a generational thing, I guess. Of course, Scrappy is also a pretty much universally reviled character, which I suppose proves that being understood isn’t always for the best.

You know who else spoke Scooby’s Canine-English pidgin? Another Hanna-Barbera dog, Astro from The Jetsons.
Mind you, that takes place in the future, so maybe his talking is a result of genetic engineering or something. Makes about as much sense as the flying car that folds up into a briefcase. I mean, is his car really light, or does some of the mass disappear when it changes shape? It’s the same issue as with some of the Transformers. Really, George Jetson’s car pretty much IS a Transfomer, albeit not a sentient one. At least as far as we know, that is.